The invention is directed to an apparatus for determining the mist concentration in a humidified air flow of a ventilating device, preferably a ventilating or air-conditioning installation.
In many areas of air treatment technology, particularly ventilating and air-conditioning installations, it is necessary to prepare the air to be used, i.e. to filter it, if necessary, to adjust its temperature and/or to influence its humidity.
The humidification of air by means of an atomizing nozzle arrangement is known. Atomizing nozzles which atomize the humidifying medium, in particular water, are arranged in a stream of air generated by positive guidance. However, there are also other alternative humidifying systems, e.g. trickling humidifiers or humidification by atomization of water by means of the impeller of a ventilator or humidification by means of centrifugal humidifiers.
An intensive mass transfer between the air and the humidifying medium is always desired in order to achieve a high humidifying efficiency with the lowest possible expenditure. However, the concentration of mist in the air (downstream of the water separator, as the case may be) should not exceed an upper limit so as not to lead to precipitation in the form of water drops so that the devices arranged downstream in the ventilating installation, e.g. a duct system, remain dry. When this degree of mist concentration is exceeded, unwanted precipitation is formed.
A water separator which separates larger drops of water from the air flow and only allows the fine mist to pass is usually arranged downstream of the humidifying apparatus. Thus, the mist concentration in the air after passing the water separator must be adjusted in such a way that precipitation of moisture is prevented on the one hand, but the mist concentration is maintained at a permissible limit on the other hand so that e.g. the cooling output of the ventilating installation is as high as possible. In so doing, the air is in a state of oversaturation; it has very small water droplets (mist) up to a determined drop size. If this drop size and a determined amount of water mist is exceeded, unwanted precipitation of moisture occurs.
The use of a moisture gauge which measures the relative air humidity, e.g. in a steam humidifier, is known for limiting mist concentration. However, there is no measuring device which can reliably measure 100% relative humidity. At best, 95% relative humidity can be reliably measured. Accordingly, the humidification output of the washer is limited only by the measuring device, since a 100% saturation of the air and a permissible amount of mist which can evaporate subsequently is impossible.
The value determined by the moisture measuring instrument is accordingly used to influence the humidifying device, e.g. the supply of water to the atomizing nozzles.
The present invention therefore has the object of providing an apparatus for determining the mist concentration in a flow of air in a ventilating device which has a simple construction and is reliable and can be installed at an .optional location downstream of the air humidifying device. This apparatus should maximize the adiabatic cooling output of a RLT installation by means of reevaporation of free droplets of mist on the one hand and, on the other hand, should prevent precipitation of water at the parts located downstream of the humidifying device which serve to guide the air.